1. Field of the Invention
The present invention relates to a microscope which is equipped with switchable objective lenses.
2. Description of the Prior Art
Microscopes which permit observing magnified images of fine samples and recording such images with photographing cameras, video cameras, etc. are widely utilized for studies and inspections in the industrial, biological and other fields of application. The microscopes which are utilized in these fields are generally equipped with a plural number of objective lenses having magnification levels different from one another and attached to a rotary revolver, which is rotated electrically or manually for switching the objective lenses to be set in an observation optical system. However, it is ordinarily impossible to observe a sample in optimum conditions through the individual objective lenses without changing the illuminated condition of the sample along with the switching of the objective lenses. Further, the conventional microscopes have a common defect that said microscopes require bringing a sample to be observed into focus each time the objective lenses are switched from one to another, thereby obliging microscopists to consume a longer time for operation of the microscopes than that usable for the studies and inspections that they desire.
In order to correct this defect, U.S. Pat. No. 4,661,692, European Patent No. 124,241 and DE 3,707,484 proposed microscopes having improved operability wherein illumination optical systems are automatically exchanged so as to establish an optimum illumination condition along with switching of the objective lenses and samples are brought into focus with automatic focusing mechanisms.
However, the above-mentioned conventional microscopes had another common defect that samples are more or less defocused by the switching operation of the objective lenses due to manufacturing variations or dimensional errors of component parts and said microscopes require refocusing of samples.